Some wonder how a 15-year old became a grandmaster. My country's highest rated GM (Wesley So) is just that age. Elo rating can jump a thousand points if that guy kept on winning games. The initial Elo rating given to players is usually wrong anyway.
Now back to the drugs topic. Neuroscience is still in it's infancy--many things are still unknown. It's not good tinkering with drugs. Caffeine is available in tablet form, someone asked if it's injectable. On a slightly diferent topic... taking megadoses of vitamins A and E is bad for the health. Just take these supplements the right way (guided by the RDA or recommended daily allowance).
"the predominant viewpoint seems to be that there is no point testing chessplayers for drugs because there is no known drug that improves your chess."
Is that also FIDE's official position on the matter?
As yet they don't do any drug tests on professional players - so I guess it is.